Why do children learn the words they do?

A review paper by linguists Nivedita Mani and Lena Ackermann looks at the factors that influence variability in early word learning.

Children learn new words slowly at first, with the majority able to produce only a handful of words by the end of their first year. But the process accelerates incredibly quickly, and by the age of 2, their vocabularies have already expanded to an average of 300 words. By the time high school graduation rolls around, they will know more than 40,000 words.

A child’s earliest words typically consist of names for caregivers (“mama”), social expressions (“bye-bye”), or common objects (“bottle”). But what factors determine the words an individual child will learn at different stages of early childhood? Why does one child know the word “bear” at 20 months, while another does not?

Psychologist and linguist Nivedita Mani at the University of Göttingen wanted to look deeper at the reasons for this type of variability in word learning. As head of the Psychology of Language Research Group, Mani studies the mechanisms underlying infant language acquisition and processing. Along with her colleague Lena Ackermann, she reviewed theories of word learning that emphasize the interaction between a child’s knowledge and own interests that help drive the learning of new words. Their conclusions were published by Child Development Perspectivesin May 2018.

“For a really long time, the standard answer to the question of why a child learns certain words first versus others was that this would depend on what children heard and saw in their environment,” said Mani. “More recently, however, there has been a spate of research looking at how much the baby herself brings to the task of language learning.”

Previous work has found that the quantity of language input directed towards children significantly affects their vocabulary size, how they process language, and future success in school. Other important factors on the caregiver side include how often we read to them, how we structure our sentences, and how much we gesticulate when we speak to them.

Since children can only learn language from hearing other people speak, it’s expected that their environment has a heavy influence on early word learning. A famous 1995 study by Betty Hart and Todd Risley reported that a 30-million-word gap exists by age 4 between children of professional parents and children of parents on welfare.

More recent research, however, emphasizes that the child also brings something to the table. In these studies, children appear to take a more active role in language acquisition by taking into account their own interests and current state of knowledge.

“Children may themselves want to learn certain things more than others, and going along the path that they choose may make them better able to learn.”

“Some of our work, for instance, looks at what kinds of words babies already know, and how this might make some babies more likely to learn some words than others,” said Mani. “There is more attention being paid to the notion that children may themselves want to learn certain things more than others, and going along the path that they choose may make them better able to learn.”

To put these results to action, caregivers can follow children’s cues with regards to what they want to talk or hear more about and pay careful attention to the topics they show interest in. Mani hopes that future research will focus on how much the different factors influencing word variability overlap to shape overall learning.

“At the big picture level, we know that we should talk to our kids — that can’t hurt, and we know that we should talk to them about what they are interested in,” she said. “But in order to bring this to a public policy context, we need to know a lot more about how to implement such learning.”